2-Oxazoline formation for selective chemical labeling of 5-hydroxylysine

Hydroxylation of lysine, one of posttranslational modifications of proteins, generates 5-hydroxylysine (Koh) and plays a crucial role in regulating protein functions in cellular activity. We have developed a chemical labeling method of Koh. The 1,2-aminoalcohol moiety of Koh in synthetic peptide sequences was trapped by an alkyne-containing benzimidate to form a 2-oxazoline ring. An additional ammonia treatment process removed the undesirable amidine residue formed between benzimidate and lysine. During the ammonia treatment, the oxazoline residue formed at Koh mainly remained intact, and the ring opening to the amide form was observed for only part of oxazoline, indicating that the chemical labeling is amino acid selective. Azide-substituted biotin or fluorescent dye was attached to the peptide through Huisgen cycloaddition at Koh and converted into an alkyne-labeled oxazoline form. The Koh-labeling assay could provide a platform to enhance proteomic research of lysine hydroxylation.

Post-translational modifications of collagen upon BMP-induced osteoblast differentiation

The pattern of collagen cross-linking is tissue specific primarily determined by the extent of hydroxylation and oxidation of specific lysine residues in the molecule. In this study, murine pre-myoblast cell line, C2C12 cells, were transdifferentiated into osteoblastic cells by bone morphogenetic protein (BMP)-2 treatment, and the gene expression of lysyl hydroxylases (LH1, 2a/b, and 3) and lysyl oxidase (LOX)/lysyl oxidase-like proteins (LOXL1-4), and the extent of hydroxylysine were analyzed. After 24h of treatment, the expression of most isoforms were upregulated up to 96h whereas LH2a and LOXL2 decreased with time. In the treated cells, both hydroxyproline and hydroxylysine were detected at day 7 and increased at day 14. The ratio of hydroxylysine to hydroxyproline was significantly increased at day 14. The results indicate that LHs and LOX/LOXLs are differentially responsive to BMP-induced osteoblast differentiation that may eventually lead to the specific collagen cross-linking pattern seen in bone.

Analysis of hydroxyproline isomers and hydroxylysine by reversed-phase HPLC and mass spectrometry

Collagens, the most abundant mammalian proteins, contain a high content of hydroxylated amino acids, such as, 3- and 4-cis-/trans-hydroxyproline (Hyp) and 5-hydroxylysine (Hyl). Whereas the global content of 4-Hyp was studied by amino acid analysis, no technique to determine all five hydroxyamino acids simultaneously in collagens has been reported. Here, we report the separation of all five hydroxyamino acids as well as two Hyp epimers from all other proteinogenic amino acids after derivatization with N(2)-(5-fluoro-2,4-dinitrophenyl)-l-valine amide (l-FDVA) by RPC-UV-ESI-MS. The general applicability of this method is shown for three Hyp-containing peptides as well as collagen type I.

Properties of collagen in OIM mouse tissues

The deletion of the alpha2 chain from type I collagen in the oim mouse model of osteogenesis imperfecta has been shown to result in a significant reduction in the mechanical strength of the tail tendon and bone tissue. However, the exact role of the alpha2 chain in reducing the mechanical properties is not clear. We now report that the stabilizing intermolecular cross-links in bone are significantly reduced by 27%, thereby contributing to the loss of tensile strength and the change in stress-strain profile. We also report that, in contrast to previous studies, the denaturation temperature of the triple helical molecule and the intact fibers are 2.6 degrees and 1.9 degrees C higher than the corresponding tail tendon collagen from wild-type mice. The increase in hydroxyproline content accounts, at least in part, for the increase in denaturation temperature. The alpha2 chain clearly plays an important part in stabilizing the type I collagen triple helix and fiber packing, but further studies are required to determine the precise mechanism.

Histomorphometric, biochemical and ultrastructural changes in the aorta of salt-loaded stroke-prone spontaneously hypertensive rats fed a Japanese-style diet

BACKGROUND AND AIM

It is demonstrated that dietary habits play a role in cardiovascular diseases. In stroke-prone spontaneously hypertensive rats (SHRsp), concomitant salt loading and a Japanese-style diet greatly accelerate hypertension and the appearance of cerebrovascular lesions by directly damaging arterial vessels. A number of studies have characterised medium and small vessel lesions in SHRsp, but little attention has been paid to the changes in the wall structure of large arteries induced by exposure to a salt-enriched diet. The aim of this study was to investigate the effects of a Japanese-style diet and salt loading on the thoracic aorta.

METHODS AND RESULTS

Two-month-old SHRsp were kept on a Japanese-style diet with 1% sodium chloride solution replacing tap water. Two months later, they were sacrificed and compared with age-matched or two-month-old control SHRsp kept on a standard diet and tap water in terms of the histomorphometry, ultrastructure and biochemical composition of the thoracic aorta. The vessel was consistently thicker in the four-month-old SHRsp (+20%, p < 0.05 vs two-month-old rats) regardless of diet. The salt-loaded SHRsp showed a significant reduction in elastic fibre density (-20%, p < 0.05 vs two-month-old rats) and an increase in the other matrix components (%), whereas the four-month-old controls showed preserved elastic fibres and a significant increase in the other matrix components (+65%, p < 0.05 vs two-month-old rats). There was a considerable increase in the amounts of 4-OH-proline (+147%), 5-OH-lysine (+174%) and desmosines (+360%) in the four-month-old controls vs their two-month-old counterparts (p < 0.01), but not in the salt-loaded animals. Ultrastructural analysis revealed clear damage and accelerated aging in the thoracic aorta of the salt-loaded SHRsp.

CONCLUSIONS

Salt loading and a Japanese-style diet destabilize thoracic aorta architecture in SHRsp after two months of treatment.

The role of the alpha2 chain in the stabilization of the collagen type I heterotrimer: a study of the type I homotrimer in oim mouse tissues

We have previously reported that the fragility of skin, tendon and bone from the oim mouse is related to a significant reduction in the intermolecular cross-linking. The oim mutation is unlikely to affect the efficacy of the lysyl oxidase, suggesting that the defect is in the molecule and fibre. We have therefore investigated the integrity of both the oim collagen molecules and the fibre by differential scanning calorimetry. The denaturation temperature of the oim molecule in solution and the fibre from tail tendon were found to be higher than the wild-type by 2.6deg.C and 1.9deg.C, respectively. With the loss of the alpha2 chain, the hydroxyproline content of the homotrimer is higher than the heterotrimer, which may account for the increase. There is a small decrease in the enthalpy of the oim fibres but it is not significant, suggesting that the amount of disorder of the triple-helical molecules and of the fibres is small and involves only a small part of the total bond energy holding the helical structure together. The difference in denaturation temperature of the skin collagen molecules (t(m)) and fibres (t(d)) is significantly lower for the oim tissues, 19.9deg.C against 23.1deg.C, indicating reduced molecular interactions and hence packing of the molecules in the fibre. Computation of the volume fraction of the water revealed that the interaxial separation of the oim fibres was indeed greater, increasing from 19.6A to 21.0A. This difference of 1.4A, equivalent to a C-C bond, would certainly decrease the ability of the telopeptide aldehyde to interact with the epsilon -amino group from an adjacent molecule and form a cross-link. We suggest, therefore, that the reduction of the cross-linking is due to increased water content of the fibre rather than a distortion of the molecular structure. The higher hydrophobicity of the alpha2 chain appears to play a role in the stabilisation of heterotrimeric type I collagen, possibly by increasing the hydrophobic interactions between the heterotrimeric molecules, thereby reducing the water content and increasing the binding of the molecules in the fibre.

Alteration of elastin, collagen and their cross-links in abdominal aortic aneurysms

OBJECTIVES

although the mechanism of arterial dilation and aneurysm development has not been clarified, the degradation of elastin and collagen plays undoubtedly a critical role. We evaluated the elastin and collagen content through the detection of their cross-links in aneurysmal and non-aneurysmal abdominal aortic walls.

MATERIALS AND METHODS

in 26 human abdominal aortic aneurysm specimens obtained during surgery and in 24 autopsy control samples of non-aneurysmal abdominal aorta the tissue content of elastin and collagen cross-links were measured by HPLC. Collagen was also detected by evaluating two characteristic amino acids, 4-hydroxyproline (4-hypro) with a colorimetric method and 5-hydroxylysine (5-hylys) by gas chromatography.

RESULTS

significantly fewer elastin cross-links were found in aneurysm samples compared to controls (desmosines and isodesmosines: 90% reduction; p<0.01). The opposite was true for pyridinoline collagen cross-links (350% increase) and deoxypyridinolines (100% increase, p=0.01). Tissue content of 5-hylys, 4-hypro and total amino acids were reduced significantly by 50% in aneurysmal samples.

CONCLUSIONS

beside confirming decreased elastin content in aneurysmal walls, these results show a concurrent increase of collagen cross-links. Since total collagen markers were decreased (decreased 4-hypro and 5-hylys) it is reasonable to suggest that in aneurysmal aortic walls old collagen accumulates cross-links while new collagen biosynthesis is somehow defective.

Development of biochemical heterogeneity of articular cartilage: influences of age and exercise

The objective of this study was to document the development of biochemical heterogeneity from birth to maturity in equine articular cartilage, and to test the hypothesis that the amount of exercise during early life may influence this process. Neonatal foals showed no biochemical heterogeneity whatsoever, in contrast to a clear biochemical heterogeneity in mature horses. The process of formation of site differences was almost completed in exercised foals age 5 months, but was delayed in those deprived of exercise. For some collagen-related parameters, this delay was not compensated for after an additional 6 month period of moderate exercise. It is concluded that the functional adaptation of articular cartilage, as reflected in the formation of biochemical heterogeneity in the horse, occurs for the most part during the first 5 months postpartum. A certain level of exercise seems essential for this process and withholding exercise in early life, may result in a delay in the adaptation of the cartilage.

Effects of phosphoric acid and glutaraldehyde-HEMA on dentin collagen

The purpose of this study was to evaluate the effects of phosphoric acid (PA) and a proprietary glutaraldehyde-HEMA aqueous solution (Gluma Desensitizer; GD) on dentin collagen. Specimens of demineralized bovine dentin collagen were treated with either 37% or 50% PA for 1 or 5 min. An additional set of specimens was treated with 37% PA for 1 min followed by GD for 1 min. All specimens were washed with distilled water, lyophilized. reduced with standardized NaB3H4, hydrolyzed with 6 M HCl and subjected to amino acid and cross-link analyses. The results demonstrated that the treatment of demineralized dentin with PA under the conditions tested did not significantly alter the collagen cross-links. The GD-treated samples showed reduction of free lysine (Lys) and hydroxylysine (Hyl) residues, as well as a decrease in the levels of collagen reducible cross-links. In addition, unidentified reducible compounds were detected by high-performance liquid chromatography (HPLC) analysis. These compounds may be derived from cross-links formed between GD-derived aldehyde and Lys/Hyl of collagen. The findings indicate that PA treatment does not significantly affect dentin collagen amino acid and cross-link composition, and that GD treatment affects dentin collagen amino acid and cross-link composition.

The influence of strenuous exercise on collagen characteristics of articular cartilage in Thoroughbreds age 2 years

In order to assess the influence of strenuous exercise on collagen characteristics of articular cartilage, the response of the collagen network was studied in seven 2-year-old Thoroughbreds subjected to strenuous exercise compared to 7 nontrained individuals. After 13 weeks, the animals were subjected to euthanasia, fetlock joints of the forelimbs were scored macroscopically after Indian Ink staining, and articular cartilage from different locations of the articular surface of the proximal first phalanx was sampled and analysed for water content, collagen content, hydroxylysine content and amount of hydroxylysylpyridinoline (HP) crosslinks. Gross lesions were significantly more severe in the exercised than in the nonexercised group. In the control animals, the characteristic site-specific differences in collagen parameters were found as described earlier, but in the strenuously exercised animals this physiological biochemical heterogeneity had disappeared. In the exercised animals, an increase in water content and a sharp decrease in HP crosslinking was found that was correlated with the presence of wear lines. It is concluded that the strenuous exercise provoked significant alterations in the characteristics of the collagen network of the articular cartilage of the fetlock joint which were suggestive of microdamage and loosening of the collagen network. The collagen component of cartilage, in contrast to the proteoglycan component, is known to have a very limited capacity for repair and remodelling due to an extremely low turnover rate. Therefore, alterations within the articular collagen network might be expected to play an important role in the pathophysiology of degenerative joint disorders.

Biological variability in assessing the clinical value of biochemical markers of bone turnover

Analytical and biological variability of three bone markers, deoxypyridinoline (DPD), CrossLaps (CTx) and galactosylhydroxylysine (GHYL) were compared. From 14 healthy subjects (six women, eight men; age 29-44 years) recruited from our laboratory staff, two sets of samples of early morning urine were obtained - four samples taken weekly for 4 weeks (all subjects) and three samples taken monthly for 3 months from five subjects. Data were expressed as the ratio to creatinine concentration. All the methods met the analytical goals (CV(A)< or =1/2CV(I(within-subject))) DPD 0.06, CTx 0.05 and GHYL 0.07 with CV(I(within-subject)) being 0.22, 0.19 and 0.38, respectively. The reference values were of limited usefulness particularly for CTx and GHYL, the index of individuality (II) being 0.50 and 0.48 respectively. As the index of heterogeneity (IH) was not significant, being 0.23 for CTx, 0.28 for DPD and 0.46 for GHYL, which are all <1.71 (1+2S.D.), within-subject variances can be used to calculate the reference change value (RCV): 0.58 for DPD, 0.54 for CTx and 1. 08 for GHYL. Moreover, we found constant variations in DPD and CTx, week to week and month to month. Our findings suggest that DPD and CTx provide more reliable results than GHYL, showing a lower within-subject variation, a lower and time-constant RCV allowing reliable monitoring without regard for timing.

Pyridinium cross-links in bone of patients with osteogenesis imperfecta: evidence of a normal intrafibrillar collagen packing

The brittleness of bone in patients with osteogenesis imperfecta (OI) has been attributed to an aberrant collagen network. However, the role of collagen in the loss of tissue integrity has not been well established. To gain an insight into the biochemistry and structure of the collagen network, the cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) and the level of triple helical hydroxylysine (Hyl) were determined in bone of OI patients (types I, III, and IV) as well as controls. The amount of triple helical Hyl was increased in all patients. LP levels in OI were not significantly different; in contrast, the amount of HP (and as a consequence the HP/LP ratio and the total pyridinoline level) was significantly increased. There was no relationship between the sum of pyridinolines and the amount of triple helical Hyl, indicating that lysyl hydroxylation of the triple helix and the telopeptides are under separate control. Cross-linking is the result of a specific three-dimensional arrangement of collagens within the fibril; only molecules that are correctly aligned are able to form cross-links. Inasmuch as the total amount of pyridinoline cross-links in OI bone is similar to control bone, the packing geometry of intrafibrillar collagen molecules is not disturbed in OI. Consequently, the brittleness of bone is not caused by a disorganized intrafibrillar collagen packing and/or loss of cross-links. This is an unexpected finding, because mutant collagen molecules with a random distribution within the fibril are expected to result in disruptions of the alignment of neighboring collagen molecules. Pepsin digestion of OI bone revealed that collagen located at the surface of the fibril had lower cross-link levels compared with collagen located at the inside of the fibril, indicating that mutant molecules are not distributed randomly within the fibril but are located preferentially at the surface of the fibril.

Functional adaptation of equine articular cartilage: the formation of regional biochemical characteristics up to age one year

Biochemical heterogeneity of cartilage within a joint is well known in mature individuals. It has recently been reported that heterogeneity for proteoglycan content and chondrocyte metabolism in sheep develops postnatally under the influence of loading. No data exist on the collagen network in general or on the specific situation in the horse. The objective of this study was to investigate the alterations in equine articular cartilage biochemistry that occur from birth up to age one year, testing the hypothesis that the molecular composition of equine cartilage matrix is uniform at birth and biochemical heterogeneity is formed postnatally. Water content, DNA content, glycosaminoglycan content (GAG) and biochemical characteristics of the collagen network (collagen content, hydroxylysine content and hydroxylysylpyridinoline [HP] crosslinks) were measured in immature articular cartilage of neonatal (n = 16), 5-month-old foals (n = 16) and yearlings (n = 16) at 2 predefined differently loaded sites within the metacarpophalangeal joint. Statistical differences between sites were analysed by ANOVA (P<0.01), and age correlation was tested by Pearson's product moment correlation analysis (P<0.01). In neonatal cartilage no significant site differences were found for any of the measured biochemical parameters. This revealed that the horse has a biochemically uniform joint (i.e. the cartilage) at birth. In the 5-month-old foals and yearlings, significant site differences, comparable to those in the mature horse, were found for DNA, GAG, collagen content and hydroxylysine content. This indicates that functional adaptation of articular cartilage to weight bearing for these biochemical parameters takes place during the first months postpartum. Water content and HP crosslinks showed no difference between the 2 sites from neonatal horses, 5-month-old animals and yearlings. At both sites water, DNA and GAG decreased during maturation while collagen content, hydroxylysine content and HP crosslinks increased. We propose that a foal is born with a uniform biochemical composition of cartilage in which the functional adaptation to weight bearing takes place early in life. This adaptation results in biochemical and therefore biomechanical heterogeneity and is thought to be essential to resist the different loading conditions to which articular cartilage is subjected during later life. As collagen turnover is extremely low at mature age, an undisturbed functional adaptation of the collagen network of articular cartilage at a young age may be of significant importance for future strength and resistance to injury.

Posttranslational modifications of bone collagen type I are related to the function of rat femoral regions

This study analyzes the relationship between the function of femoral regions in the rat and the extent of collagen type I posttranslational modifications, to assess whether the different functional roles, i.e., mechanical or metabolic, of the bone tissues are related to the molecular structure of the matrix. For this purpose, 18 female, 100-day-old Sprague-Dawley rats were sacrificed, under anesthesia, and their femurs were removed and dissected free of adhering tissue. The spongy bone of the proximal metaphysis and the diaphysis were then selected as regions exerting prevalently a mechanical function, and the spongy bone of the distal metaphysis was selected as mainly related to metabolic function. Bone prepared from these regions was used to extract and purify the major component of the matrix, type I collagen. The content of hydroxyproline, hydroxylysine, glycosylated hydroxylysine, and pyridinium crosslinks was evaluated and the amount of each compound was expressed as a molar ratio to hydroxyproline. The amount of glycosylated hydroxylysine and pyridinium crosslinks in the distal metaphysis are significantly different from the amounts measured both in the diaphysis and the proximal metaphysis. On the contrary, the amounts of the same compounds in the diaphysis and the proximal metaphysis are statistically the same. The amount of free hydroxylysine, however, appears to be different in the proximal metaphysis and in the diaphysis. The conclusion is that matrix composition differs among different skeletal regions according to the main function they exert.

A rapid and simple method for quantitation of urinary hydroxylysyl glycosides, indicators of collagen turnover, using liquid chromatography/tandem mass spectrometry

Some glycosides of hydroxylysine, viz., alpha-1, 2-glucosylgalactosyl-O-hydroxylysine and beta-1-galactosyl-O-hydroxylysine, appear to be good indicators of collagen turnover. A simple liquid chromatography/tandem mass spectrometry (LC/MS/MS) method is proposed for measuring these analytes in urine, with no sample preparation except for a dilution step. Quantitation is performed using external calibration with no internal standard. A preliminary survey indicates good intra- and inter-day reproducibility (better than 5 and 8%, respectively). With the present method, the estimated limits of detection (S/N > 3) in urine are 0.8 and 0.5 microM/L for beta-1-galactosyl-O-hydroxylysine and alpha-1,2-glucosylgalactosyl-O-hydroxylysine, respectively. The method is proposed as a robust tool for a large-scale research investigation on collagen turnover.

Topographical mapping of biochemical properties of articular cartilage in the equine fetlock joint

The aim of this study was to evaluate topographical differences in the biochemical composition of the extracellular matrix of articular cartilage of the normal equine fetlock joint. Water content, DNA content, glycosaminoglycan (GAG) content and a number of characteristics of the collagen network (total collagen content, levels of hydroxylysine- (Hyl) and the crosslink hydroxylysylpyridinoline, (HP) of articular cartilage in the proximal 1st phalanx (P1), distal 3rd metacarpal bone (MC), and proximal sesamoid bones (PSB) were determined in the left and right fetlock joint of 6 mature horses (age 5-9 years). Twenty-eight sites were sampled per joint, which included the clinically important areas often associated with pathology. Biochemical differences were evaluated between sampling sites and related with the predisposition for osteochondral injury and type of loading. Significant regional differences in the composition of the extracellular matrix existed within the joint. Furthermore, left and right joints exhibited biochemical differences. Typical topographic distribution patterns were observed for each parameter. In P1 the dorsal and palmar articular margin showed a significantly lower GAG content than the more centrally located sites. Collagen content and HP crosslinks were higher at the joint margins than in the central area. Also, in the MC, GAG content was significantly lower at the (dorsal) articular margin compared with the central area. Consistent with findings in P1, collagen and HP crosslinks were significantly lower in the central area compared to the (dorsal) articular margin. Biochemical and biomechanical heterogeneity of articular cartilage is supposed to reflect the different functional demands made at different sites. In the present study, GAG content was highest in the constantly loaded central areas of the joint surfaces. In contrast, collagen content and HP crosslinks were higher in areas intermittently subjected to peak loading which suggests that the response to a certain type of loading of the various components of the extracellular matrix of articular cartilage are different. The differences in biochemical characteristics between the various sites may help to explain the site specificity of osteochondral lesions commonly found in the equine fetlock joint. Finally, these findings emphasise that the choice of sampling sites may profoundly influence the outcome of biochemical studies of articular cartilage.

Recombinant human type II collagens with low and high levels of hydroxylysine and its glycosylated forms show marked differences in fibrillogenesis in vitro

Type II collagen is the main structural component of hyaline cartilages where it forms networks of thin fibrils that differ in morphology from the much thicker fibrils of type I collagen. We studied here in vitro the formation of fibrils of pepsin-treated recombinant human type II collagen produced in insect cells. Two kinds of type II collagen preparation were used: low hydroxylysine collagen having 2.0 hydroxylysine residues/1,000 amino acids, including 1.3 glycosylated hydroxylysines; and high hydroxylysine collagen having 19 hydroxylysines/1,000 amino acids, including 8.9 glycosylated hydroxylysines. A marked difference in fibril formation was found between these two kinds of collagen preparation, in that the maximal turbidity of the former was reached within 5 min under the standard assay conditions, whereas the absorbance of the latter increased until about 600 min. The critical concentration with the latter was about 10-fold, and the absorbance/microgram collagen incorporated into the fibrils was about one-sixth. The morphology of the fibrils was also different, in that the high hydroxylysine collagen formed thin fibrils with essentially no interfibril interaction or aggregation, whereas the low hydroxylysine collagen formed thick fibrils on a background of thin ones. The data thus indicate that regulation of the extents of lysine hydroxylation and hydroxylysine glycosylation may play a major role in the regulation of collagen fibril formation and the morphology of the fibrils.

Assay for 5-hydroxylysine and L-lysine in human and rat urine and in bone by gas chromatography

An accurate method for the determination of collagen to study its distribution and turn-over in different tissues is described. 5-Hydroxylysine (5Hylys) is an amino acid that is apparently present in no other protein except collagen and, as it is metabolised only to a minor degree compared with 4-hydroxyproline (4Hypro), it has been suggested as a better marker of the collagen metabolism. Interest in this amino acid has increased recently because the levels of 5Hylys in urine and in different tissues may offer a new basis for detecting pathologies of the collagen molecule. This paper describes a method for the quantitative determination of 5Hylys and lysine (Lys) by gas chromatography (GC) in human and rat urine and in rat bone. The limit of detection was 350 pmol ml-1 for 5Hylys and 200 pmol ml-1 for Lys for all the biological samples. This method therefore provides a complete view of the metabolism of this amino acid and of the tissue it comes from.

Influence of different chemical cross-linking treatments on the properties of bovine pericardium and collagen

The use of biological materials in the construction of bioprostheses requires the application of different chemical or physical procedures to improve the mechanical performance of the material without producing any undesirable effects. A number of cross-linking methods have been tested in biological tissues composed mainly of collagen. The basis for most of them is the use of glutaraldehyde (GA), which acts on the Lys or Hyl residues. We have studied the effects of alternative chemical treatments: diphenylphosphorylazide (DPPA) and ethyldimethylaminopropyl carbodiimide (EDAC). Their mechanism of action is based on the activation of the carboxyl groups, which then permits their cross-linking to amino groups. As a control, we employed conventional treatment with GA, applying it to bovine pericardium and collagen membranes removed from bovine pericardium. The analysis of the Lys and Hyl residues showed that DPPA and EDAC produced 50% of the chemical change provoked by GA. This value was even lower in the trials with collagen. In terms of the resistance to collagenase degradation, chemical cross-linking with GA provided much greater protection in both materials (3.81 +/- 3.47 nmol of amino acid/mg dry tissue for pericardium and 4.41 +/- 1.13 nmol of amino acid/mg dry tissue for collagen). Treatment with DPPA also protected pericardium (13.11 +/- 6.57 nmol amino acid/mg dry tissue) although the values for collagen was lower (50.0 +/- 32.4 nmol amino acid/mg dry tissue). Treatment with EDAC was much less protective than the other two chemical reagents (43.28 +/- 17.4 and 55.85 +/- 14.57 nmol amino acid/mg dry tissue for pericardium and collagen, respectively). The degree of tissue calcification after implantation of the chemically treated materials into young rats was considerably greater for GA and DPPA (32.9 +/- 18.8 and 36.3 +/- 13.3 mg g(-1) dry tissue, respectively) than with EDAC (18.0 +/- 7.2 mg g(-1) dry tissue; P < 0.001). After 60 days of implantation, the values for GA and EDAC were higher(124.1 +/- 31.3 and 124.6 +/- 21.0 mg g(-1) dry tissue, respectively) versus 34.6 +/- 19.2 mg g(-1) dry tissue for DPPA. There were no significant differences in collagen levels in samples treated with GA or EDAC after 30 days of implantation, although both groups showed significant differences when compared with DPPA-treated samples (P < 0.001). After 60 days of implantation, there were no significant differences among these three treatments in terms of the calcium accumulated on samples.

Altered posttranslational modifications of collagen in keloid

Keloid is a tissue with an excessive accumulation of collagen. In this study, we have partially characterized post-translational modifications of type I collagen in human keloid in order to pursue their potential involvement in this pathology. The levels of lysyl hydroxylation of the helical portions of alpha 1 and alpha 2 chains of type I collagen in keloid were significantly higher than those of normal, while the levels of prolyl hydroxylation were identical between these two groups. The contents of the major reducible cross-links in dermal collagen, dehydro-hydroxylysinonorleucine and dehydro-histidinohydroxymero-desmosine, were both significantly higher in keloids (up to sixfold) than those of normal. In addition, significant amounts of hydroxylysine-aldehyde derived cross-links that are characteristic of skeletal tissue collagens, dehydro-dihydroxylysinonorleucine (about 0.3 mole/mole of collagen) and pyridinoline (about 0.1 mole/mole of collagen), were found in keloids. These results indicate that keloid-forming cells are phenotypically different from those in normal dermis and that the collagen produced is highly cross-linked. The increased cross-linking provides the fibrils with more stability that may result in an accumulation of collagen.

Ultraviolet exposure influences laser-induced wounds, scars, and hyperpigmentation: a murine study

Laser therapy is today considered the treatment of choice for vascular skin lesions, which commonly are located on the face and, therefore, frequently are exposed to sunlight. The purpose of this study was to examine whether preoperative and postoperative ultraviolet irradiation influences the development of laser-induced side effects. We laser-treated hairless mice with a copper vapor laser; three different intensities were used at a constant pulse duration. Simulated solar ultraviolet radiation was administered either before the laser treatment (3 consecutive days, daily doses of 2.48 J/cm2) or after the laser treatment (four times weekly in 4 weeks, daily doses of 1.66 J/cm2). Laser-induced wounds, scars, and hyperpigmentation were evaluated by macroscopic, histologic, and biochemical examinations. Preoperative ultraviolet exposure enlarged the laser-induced wounds and the areas with texture change at some of the laser intensities used. However, the most pronounced effect was seen for postoperative ultraviolet-irradiated mice. These mice developed, at some of the laser intensities, a higher incidence of bulging infiltration as well as higher degrees of fibrosis and hyperpigmentation, thus developing a poor cosmetic appearance. Furthermore, ultraviolet irradiation after laser treatment resulted in slowly healing wounds of reduced size, indicating deep, constricted skin damage. We conclude that ultraviolet exposure before and after copper vapor laser treatment increases the risk of inducing side effects from dermatological laser treatment.

Expression and characterization of recombinant human type II collagens with low and high contents of hydroxylysine and its glycosylated forms

Insect cells coinfected with two baculoviruses, one coding for the pro alpha chains of human type II procollagen and the other for both the alpha and beta subunits of human prolyl 4-hydroxylase, produced the cartilage-specific type II collagen with a stable triple helix. The highest expression levels, up to 50 mg/l of type II collagen, were obtained in suspension culture using a modified construct in which sequences coding for the signal peptide and N propeptide of type II procollagen had been replaced by those for type III procollagen. The type III N propeptide artificially generated into type II procollagen was found to be cleaved at a much higher rate than the wild-type type II N propeptide, probably because the former interacted poorly with the triple-helical domain of type II procollagen. The amino acid composition of the recombinant type II collagen was very similar to that of the non-recombinant protein, but the hydroxylysine content was only 17% and that of glycosylated hydroxylysines was equally low. The hydroxylysine content was increased to the level found in the non-recombinant collagen by using an additional baculovirus coding for lysyl hydroxylase, and a substantial increase was also found in the glycosylated hydroxylysine content. No difference in thermal stability was found between the low- and high-hydroxylysine collagens.

Pre-column derivatisation method for the measurement of glycosylated hydroxylysines of collagenous proteins

Measurement of the glycosylated hydroxylysines galactosyl- and glucosylgalactosylhydroxylysine (GH and GGH) in combination with other amino acids has been based on ion-exchange chromatography followed by reaction with ninhydrin. Here, a rapid and sensitive high-performance liquid chromatographic method with fluorimetric detection has been developed and employed to determine the glycosylated hydroxylysine residues in alkaline collagen hydrolysates. After hydrolysis, amino acids were derivatised with 9-fluorenylmethyl chloroformate and separated on a Micropak ODS-80TM reversed-phase column (150x4.6 mm). With a multistep gradient system all amino acids were separated in less than 30 min, including the collagen-specific hydroxylysine, hydroxyproline and the glycosylated hydroxylysines. The method was used to evaluate the glycosylation levels of human articular cartilage derived from femoral head, femoral condyle, tibial plateau and ankle. GGH was highest in cartilage from femoral head and ankle; GH showed no differences between the different sources of cartilage.

[Structural-functional UV-modifications of C1q factor of the human complement system]

The structural transformations of C1q-protein induced by the UV-light at doses 151 and 2265 J/m2 has been determined by means of acid-basic titration, IR- ans UV-spectrophotometry. These transformations are stipulated by unfolding of its molecules without change of the secondary structure types ratio and accompanies by exposition on aromatic amino acid residues as well as glutamine and asparagine acids, lysine, hydroxylysine and cysteine on the globule surface. The correlation between structural photomodifications and processes of functional activation of C1q has been established.

Comparative biochemical analysis of sea urchin peristome and rat tail tendon collagen

We report here a biochemical comparison between type 1 rat tail tendon collagen and collagen isolated from sea urchin peristome tissue. The sea urchin collagen consisted of two species of apparent mol masses, 140 and 116 kDa. Amino acid compositional analysis of the 140 and 116 kDa species revealed the presence of hydroxyproline and hydroxylysine as well as a glycine content of 28.1 mol.%. In solubility experiments the rat tail tendon collagen was found to precipitate at sodium chloride concentrations between 1 and 2 M while peristome collagen remained soluble at salt concentrations as high as 4 M. Incubation of the peristome and rat tail tendon collagen preparations with a sea urchin collagenase/gelatinase resulted in cleavage of the former but not the latter collagen. Upon heat denaturation at 60 degrees C, however, the rat tail tendon collagen served as a substrate for the gelatinase. Cyanogen bromide cleavage of rat tail and peristome collagens generated largely unique peptide maps. Collectively, these results suggest that structural differences exist between echinoderm and vertebrate type 1 collagens.

Chemistry of collagen cross-linking: biochemical changes in collagen during the partial mineralization of turkey leg tendon

With age, the proximal sections of turkey leg tendons become calcified, and this phenomenon has led to their use as a model for collagen mineralization. Mineralizing turkey leg tendon was used in this study to characterize further the composition and cross-linking of collagen in calcified tissues. The cross-link profiles of mineralizing collagen are significantly different from those of other collagenous matrices with characteristically low amounts of hydroxylysyl-pyridinoline and the presence of lysyl-pyridinoline and pyrrolic cross-links. However, the presence of the immature cross-link precursors previously reported in calcifying tissues was not supported in the present study, and was found to be due to the decalcification procedure using EDTA. Analysis of tendons from young birds demonstrated differences in the cross-link profile which indicated a higher level of hydroxylation of specific triple-helical lysines involved in cross-linking of the proximal tendon. This may be related to later calcification, suggesting that this part of the tendon is predestined to be calcified. The minimal changes in lysyl hydroxylation in both regions of the tendon with age were in contrast with the large changes in the cross-link profile, indicating differential hydroxylation of the helical and telopeptide lysine residues. Changes with age in the collagen matrix, its turnover and thermal properties in both the proximal and distal sections of the tendon clearly demonstrate that a new and modified matrix is formed throughout the tendon, and that a different type of matrix is formed at each site.

Semipreparative isolation of collagen types I, II, III and V by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electroelution

A simple method for the isolation of alpha-chains of different collagen types was developed. The procedure involves sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroelution of separated and defixed collagen alpha-chains. Collagen types I, II, III and V from different porcine tissues were recovered in high quantity (> 95%) and purity (> 98%) as evidenced by amino acid analysis. The procedure can be used for sample quantities smaller than required for conventional methods e.g. chromatographic procedures.

Possible changes in secondary structure and composition of human lens capsules in hereditary congenital cataract

BACKGROUND

Scanty information is available on the changes in conformational structure and composition of human lens capsule in cases of hereditary congenital cataract. The purpose of this study was to use Fourier-transformed infrared (FT-IR) spectroscopy to determine the secondary structure and composition of hereditary cataractous human lens capsule, as compared with normal human lens capsule.

METHODS

FT-IR spectroscopy with the Fourier self-deconvolution and curve-fitting program was performed, and second-derivative analysis was used to verify the peak positions and assignments of the IR spectra.

RESULTS

The curve-fit FT-IR spectra revealed that the content of hydroxylysine and arginine were clearly higher in the lens capsule of the hereditary congenital patient, but the content of aspartic acid significantly lower, than in normal human lens capsules. The secondary conformational changes in alpha-helix, triple helix and random coil structures were important findings in the lens capsule of a hereditary cataractous patient.

CONCLUSION

Possible alterations in secondary structures and compositions of lens capsule are observed in the hereditary congenital cataractous patient by using FT-IR spectroscopy with curve-fitting and second-derivative analysis.

Type X collagen isolated from the hypertrophic cartilage of embryonic chick tibiae contains both hydroxylysyl- and lysylpyridinoline cross-links

Hypertrophic cartilage from the tibiotarsus of Day 20 chick embryonic tibiae was found to contain an unusually high concentration of lysylpyridinoline (LP), a nonreducible collagen cross-link normally found only in bone and dentin but not in cartilage. Since type X collagen is abundant in this cartilage, research was conducted to see if type X was the primary source of LP. The 45-kDa pepsin-resistant form of type X was purified by immunoaffinity chromatography. It contained a high concentration of the LP cross-link while type II contained primarily hydroxylysylpyridinoline (HP), the predominant cross-link in cartilage. This, to our knowledge is the first time that type X has been shown directly to form nonreducible cross-links and that a collagen other than type I has a high level of LP. Also, it is interesting that the HP and LP cross-links are found in a collagen that is degraded so rapidly. Possible explanations for these findings are discussed.

Biochemical changes in the collagenous matrix of osteoporotic avian bone

No detailed biochemical analysis has been carried out of the compositional changes in the collagen matrix of avian bone in relation to increased bone fragility in osteoporosis. We have shown that osteoporosis in avian bone is certainly not just a simple loss of apatite and collagen, but involves significant changes in the biochemistry of the collagen molecule and consequently in the physical properties of the fibre. The decreased mechanical strength and the change in the thermal stability can be directly related to changes in post-translational modifications, i.e. lysine hydroxylation and the intermolecular cross-link profile. The increased hydroxylation and change in cross-linking are consistent with increased turnover of the collagen, possibly in an attempt to initiate a repair mechanism which, in fact, leads to an acceleration in the increase in fragility of the bone. Clearly there are post-translational modifications of the newly synthesized collagen in avian osteoporosis, and these changes may play a role in the pathogenesis of the disease.

Hydroxylation of collagen type I: evidence that both lysyl and prolyl residues are overhydroxylated in osteogenesis imperfecta

The composition of the collagens secreted into the media of fibroblast cultures of 39 patients with osteogenesis imperfecta (OI) was the same in controls and OI cultures. An abnormal migration pattern of collagens upon SDS-PAGE was evident in one third of the cultures investigated. Lysyl and prolyl hydroxylation of HPLC-purified alpha 1(I) chains was elevated in about 60% of cultures. The degree of hydroxylation was highest in the lethal forms. The extent of lysyl and prolyl hydroxylation showed a strong correlation (r = 0.74, P < 0.001). While high levels of hydroxylation are frequently observed in OI patients, a direct correlation between lysyl or prolyl hydroxylation and fracture rate or growth retardation could not be established.

Collagen synthesis in (sun-) aged human skin and in fibroblasts derived from sun-exposed and sun-protected body sites

Endogenous and sun-induced aging of the skin cause distinct morphological alterations. In this study, we have analysed the ratio of collagen III to collagen III plus I in extracts of sun-exposed (face) and sun-protected (abdomen) aged skin, as well as in collagens synthesized by fibroblasts during in vitro culture derived from actinically damaged and sun-protected skin of other subjects (face, medial aspect of the upper arm vs. abdomen, lateral aspect of the forearm). Furthermore, the amount and extent of post-translational modifications of newly synthesized collagens were determined. Chronic sun exposure of the skin does not have an impact on the quantity of collagenous proteins newly synthesized in cell culture. The proportion of collagen III in pepsin extracts of sun-damaged skin is increased relative to sun-protected skin. However, fibroblasts derived from sun-exposed skin synthesize a lower proportion of collagen III than cells from sun-protected skin. The hydroxylation of lysyl residues in newly synthesized alpha 2(I) and alpha 1(III) collagen chains is reduced by UV irradiation, whereas hydroxylation of lysyl residues in alpha 1(I) chains and of prolyl residues in alpha 1(I), alpha 2(I) and alpha 1(III) chains is unaffected by UV irradiation. These data provide circumstantial evidence to indicate that collagen synthesis is influenced independently by endogenous and sun-induced aging.

Biochemical markers of bone turnover for the clinical assessment of bone metabolism

Despite these potential problems, biochemical bone markers are the single most sensitive method for monitoring acute changes in bone metabolism. For example, subcutaneous injections of recombinant human insulin-like growth factor I cause a measurable increase in both procollagen and urinary DPD in as little as 1 day. Similarly, it is possible to measure a significant decrease in bone formation as determined by decreases in serum levels of ALP, OC, and C-PCP within 12 hours after the beginning of a PTH infusion study. Additionally, an increase in DPD/cr was determined within 24 hours of the start of bed rest. These changes, seen within 24 hours, are far earlier than could be detected by any other method of monitoring bone metabolism. Thus, biochemical assays have opened a new era where changes in bone metabolism can be detected in hours to days. This acute detectability should be especially helpful to the development of new drugs and the optimization of the use of approved drugs. Accordingly, definite dose-response studies can now be done in a reasonable time. For osteoporosis therapy there are reasons to consider cyclic drug administration, such as avoiding drug resistance (PTH or calcitonin), avoiding overtreatment (bisphosphonates), or avoiding a possible mineralization defect (fluoride). By using biochemical assays, we can determine the optimum amount of "on time" and "off time" in cyclic therapy. Of the bone formation assays, ALP, OC, and PCP, we recommend for routine use the OC assay because of its high discriminant power and because it has been better characterized, in terms of clinical application, than the PCP assays and the ALP IRMA. If, however, the serum cannot be drawn at a specific time in all patients to be studied, we recommend the ALP assay because, unlike the OC assay, it shows no diurnal variation. Of the bone resorption assays, HYP, TRAP, GHYL, and PYD/DPD, we recommend the urine PYD/DPD assay (adjusted for creatinine) because it is commercially available and because, along with the urine GHYL assay, it is the most sensitive bone resorption assay. Established guidelines for the use of assays in patient care is not yet available, largely because of the large intrapatient variation seen with most assays. Once this problem is resolved, it should be possible to apply biochemical assays to routine clinical practice. For example, if the patient has a urine DPD/cr (indicating a high bone resorption rate), the patient would be selected for antiresorptive therapy, and subsequently the urine DPD/cr assay would be repeated during therapy to determine the effective dose of the drug.(ABSTRACT TRUNCATED AT 400 WORDS)

Rat cortical and trabecular bone collagen glycosylation are differently influenced by ovariectomy

This study sought to evaluate whether estrogen depletion influences the hydroxylysine glycosydes content of rat bone collagen. For this reason thirty 100 day old female rats were divided in 6 groups of 5 rats each. Three groups were ovariectomized and 3 groups were sham-operated. The animals were sacrificed at 115, 130 and 145 days of age (i.e., 15, 30 and 45 days after surgery). Cortical and trabecular bone was prepared from tibiae and femurs. Hydroxylysine glycosydes content was measured by HPLC. Ovariectomy is followed, in the rat, by an increased hydroxylysine glycosylation in trabecular bone but by a constant or slightly decreased hydroxylysine glycosylation in the cortical bone. In view of the different effects of estrogens on the two bone compartments previously reported, a possible functional explanation of these findings is proposed.

Side effects of laser therapy, modified by ultraviolet irradiation and para-aminobenzoic acid in mice

Scarring is a well-known side-effect of cutaneous laser treatment and exposure to solar ultraviolet radiation is suspected to increase scar formation. We investigated how wounds and scarring were modified by interfering in the laser-induced inflammation using ultraviolet radiation and para-aminobenzoic acid. A copper vapour laser operating at 578 nm was used at three different intensities and doses. The ultraviolet radiation was administered three times weekly prior to and four times weekly after the laser treatment. The daily dose was 21.5 kJ/m2 equivalent to 3.5 Basic-MED. The laser-induced wounds were evaluated daily and histological and biochemical analyses were used to estimate scarring. Ultraviolet irradiation resulted at some of the used laser intensities in decreased scores of maximum wound area, wound healing time, cumulated wound area, and a decreased skin content of hydroxyproline, whereas the degree of the chronic fibrosis tended to increase. Application of para-aminobenzoic acid before the solar ultraviolet irradiation did not change the acute wound scores but reduced, although not significantly, the degree of fibrosis.

Laser induced wounds and scarring modified by antiinflammatory drugs: a murine model

Scarring is a well-known side effect to cutaneous laser treatment. Therefore we investigated if wounds and scarring could be decreased by pharmacological interference in the acute inflammatory reaction following laser therapy. A copper vapor laser operating at 578 nm was used at three different intensities and doses. The antiinflammatory drugs methylprednisolone (1 mg/kg/24 h) and indomethacin (2 mg/kg/24 h) were administered through the drinking water. The laser induced wounds were evaluated daily and histologic and biochemical analyses were used to estimate scarring. The administration of antiinflammatory drugs resulted at some laser intensities in increased scores of maximum wound area, healing time, cumulated wound area, fibrosis, hydroxyproline, and hydroxylysine, being mostly pronounced for indomethacin at 0.8 W/spot. The maximum wound area and the wound healing time could be used as a predictor of scarring. A dose response was shown between the laser intensities and the mentioned parameters. We recommend carefulness in the laser treatment of patients receiving indomethacin and disrecommend use of the drug in the prophylaxis against laser induced scarring.

Post-translational modifications in the collagen of human osteoporotic femoral head

No detailed biochemical analysis has been made of the possible compositional changes in the collagen relating to the fragility of osteoporotic bone. We report for the first time significant changes in the compositional properties of the collagen. The major differences were observed in the post-translational modifications, namely, in the hydroxylation of lysine residues and the nature of the stabilizing cross-links of the collagen fibre. The increase in hydroxylation was greater in the head region compared to the neck region of the femoral head, whilst the decrease in the intermediate cross-links was greater in the neck region. Clearly, the collagen is altered in osteoporosis and it is important that these changes are recognised in studies of bone metabolism in osteoporosis since they may play a role in the pathogenesis of the disease.

Amino acid composition of dentine in permanent human teeth

Dentine of permanent mandibular incisors from nine individuals was hydrolysed and the amino acid composition determined by ion-exchange chromatography against a standard calibrant of 41 amino acids. Nineteen amino acids were detected, including small quantities of 1-methylhistidine and asparagine, two amino acids whose existence had apparently not been recorded before in human dentine. The total content of hydroxylysine plus lysine varied between 2.6 and 3.3 residues per 100 (SD, 0.74) in different teeth, which therefore did not support previous studies that had proposed a constant total value. This and other quantifiable differences between present and previous findings may be the result of the different methods and the influence of dietary and other regional factors on dentinogenesis.

Quantitative analysis of collagen content and amino acids in trabecular meshwork

The purpose of this study was to compare collagen content in the TM of normal and glaucomatous eyes, and to establish whether collagen levels change with age. Collagen content was measured in 30 normal and 27 age matched glaucoma trabeculectomy specimens by the sirius red dye binding technique, and in 14 normal and 15 age matched glaucoma specimens by amino acid analysis. Both dye binding data and amino acid analysis showed no statistical difference between normal and glaucoma samples. Age had no significant effect on mean optical densities or on the collagen-specific amino acids proline, hydroxyproline, and hydroxylysine. Amino acid variability, however, was statistically different between the two groups. These results indicate that mean collagen levels in the trabecular meshwork of glaucomatous eyes do not differ from those in normal eyes.

Early markers of lung injury

The goal of this study was to develop an early marker of lung injury that might change in response to exposure to a mobile source emission. Nitrogen dioxide (NO2)2 was chosen as an example of an atmospheric pollutant that is related to automobile emissions. Since reorganization of the connective tissue matrix of the lung occurs in response to injury, markers of connective tissue metabolism were selected as targets. Hydroxylysine became the marker of choice. It is an amino acid that is virtually exclusive to collagen, although it does occur in minimal amounts in other proteins. Furthermore, it is excreted in the urine, which makes it readily available for analysis using noninvasive techniques. Other markers evaluated as part of the study included angiotensin-converting enzyme as a marker of lung injury, desmosine as a marker of elastin degradation, and hydroxyproline as another marker of collagen metabolism. Male Fischer-344 rats were exposed in whole-body chambers to controlled concentrations of NO2 for various doses and periods of time. The concentrations of NO2 ranged from 0.5 to 30 parts per million (ppm); the rats were exposed for six hours per day for periods of two days to four weeks. Urine and bronchoalveolar lavage samples were collected and analyzed for the appropriate marker. In addition, pulmonary function studies and histologic examinations of the lungs were completed at selected time points. Urinary hydroxylysine concentration increased as a function of NO2 concentration during six-hour-per-day exposures for two days. This short-term exposure required relatively high doses to achieve significant changes in the hydroxylysine output. During one-week exposures to either 25 or 30 ppm NO2, there was an increase in urinary hydroxylysine associated with changes in lavage concentrations of angiotensin-converting enzyme and hydroxylysine. The lungs of these animals demonstrated histologic changes typical of oxidant injury. Four-week exposure protocols using 0.5 and 1 ppm NO2 were most interesting in terms of the sensitivity of the marker. There was minimal damage revealed by the histology and function studies, yet there were significant increases in the excretion of hydroxylysine. It appears that hydroxylysine can be indicative of exposure when other parameters are normal. It will require long-term follow-up of exposed rats to determine whether or not the change in marker concentration is predictive of damage. Hydroxylysine may be an excellent marker of exposure to oxidants in the human population. Controlled studies to establish base-line values are needed, followed by carefully controlled studies in individuals with connective tissue abnormalities of the lung.

Pinpointing the sites of hydroxylysine glycosides in peptide alpha 1-CB7 of bovine corneal collagen, and their possible role in determining fibril diameter and thus transparency

Two cyanogen bromide fragments (alpha 1-CB7 and alpha 1-CB8) of bovine corneal stromal collagen have been isolated and characterized. These added to those characterized in our previous work account for 95% of the amino acid sequence of the alpha 1(1)-chain. The hydroxylysine glycoside content of each fragment was determined and in this way the general distribution of glycoside over the entire molecule was deduced accounting for all the galactosylhydroxylysine and most of the glucosylgalactosylhydroxylysine of this heavily glycosylated type I collagen. The characterization of fragments alpha 1-CB7 and alpha 1-CB8 has enabled us to resolve the controversy over the relative mobilities of these fragments on SDS gels. Fragment alpha 1-CB7 of bovine corneal collagen was digested by trypsin and by staphylococcal proteinase V8. The resultant peptides were isolated by gel and ion-exchange chromatography and identified in relation to the known amino acid sequence of type I collagen. The hydroxylysine glycosides were determined in the relevant peptides providing a complete account of their distribution along this part of the collagen molecule. Most of the glycoside was found in the gap region of collagen especially near the edges of the axial holes where it could act as a peg to facilitate fibre formation. In addition, some glycoside was found in the overlap region where, being unable to fit into axial holes, it might impede the growth of the fibre and, with other glycoside of the overlap region, might be responsible for the narrow fibres of corneal collagen that are essential for corneal transparency. This glycoside, with that previously found in the peptide alpha 1-CB3 is the only hydroxylysine glycoside identified in the overlap region of a type I collagen.

Improved method for amino acid analysis of stained collagen bands from polyacrylamide gels using high-performance liquid chromatography

A procedure is described for the determination of the amino acid composition of stained collagen bands separated by sodium dodecyl sulphate polyacrylamide gel electrophoresis using high-performance liquid chromatography and post-labelling with o-phthalaldehyde. Six alpha-chain bands from collagens I, III and V were analysed directly after gel electrophoresis, Coomassie blue staining and destaining. It was shown that good accuracy and reproducibility can be attained using this method, which makes it possible to determine simultaneously nineteen amino acids: Asx, Thr, Ser, Glx, Pro, Cys, Gly, Ala, Val, Met, Ile, Leu, Tyr, Phe, His, Lys and Arg together with 4-Hyp and Hyl, specific amino acids found in collagen.

Determination of myofibrillar and connective tissue protein contents of young and adult avian (Gallus domesticus) skeletal muscles and the N tau-methylhistidine content of avian actins

The myosin, actin, and collagen contents of young and adult avian red (leg) and white (breast) skeletal muscles from White Leghorn chickens have been determined by the use of analytical chromatographic methods developed to quantify the unique amino acids that occur in these proteins. Because one mole of actin purified from the red and white muscles of Leghorn chickens and one mole of myosin contain respectively one and two moles of N tau-methylhistidine, and the molar ratio of myosin and actin in skeletal muscle is known to be 1:6, the myofibrillar myosin and actin contents of avian skeletal muscles can be determined from the amounts of protein-bound N tau-methylhistidine found in acid hydrolysates of this tissue. Actin accounts for an estimated 11.2 to 12.2% of total muscle mass in both muscles or about 21.1% of total myofibrillar protein, whereas myosin ranges from 23.4 to 25.8% of total protein, corresponding to a mean value of 43.8% of total myofibrillar proteins. Total avian collagen ranged from 1.96 to 3.08% in breast and from 5.63 to 6.87% in leg skeletal muscles. With the methods described herein, content of collagen and collagen-like proteins can be calculated from amounts of 5-hydroxylysine present. The content of total connective tissue proteins could also be calculated from amounts of 4-hydroxyproline found. These quantifications are based on total protein content of the selected avian muscles determined by their detailed amino acid composition.

Nonenzymatic glycation of basement membranes from human glomeruli and bovine sources. Effect of diabetes and age

The nonenzymatic glycation of glomerular basement membranes (GBMs) from 14 diabetic and 19 nondiabetic human subjects was determined after boronic acid affinity and high-performance cation-exchange chromatography of their NaB[3H]4-reduced ketoamine adducts. The glucitol-lysine (Glc-Lys) and the glucitol-hydroxylysine (Glc-Hyl) content of diabetic GBM was found to be about twofold higher than that of nondiabetic samples (P less than .001). The content of these glycated amino acids did not correlate with age over the range examined (20-91 yr) or with the length of disease in diabetic subjects (2-16 yr). However, analyses of Glc-Lys and Glc-Hyl in calf and adult bovine GBM and lens capsules indicated that the levels of these glycated amino acids were several times greater in basement membranes from older animals. We also observed that guanidine-insoluble collagen of bovine GBM is more extensively glycated (approximately 4-fold) than primarily noncollagenous proteins that are extracted by this reagent. In all of the basement membranes examined, the percentage of glycation of lysine was greater than of hydroxylysine. Characterization of the components released by alkaline hydrolysis indicated that O-glycosylated hydroxylysine residues are nonenzymatically N-glycated to the same extent as those without an enzymatically attached carbohydrate unit. Our study indicates that more than a hundred times as many hydroxylysine residues are enzymatically glycosylated in human and bovine GBM as those containing the nonenzymatically formed ketoamine adduct.

Identification of the post-translational modifications of the core-specific lectin. The core-specific lectin contains hydroxyproline, hydroxylysine, and glucosylgalactosylhydroxylysine residues

The core-specific lectin (CSL) synthesized and secreted by rat hepatocytes and the rat hepatoma H-4-II-E shows affinity for mannose and N-acetylglucosamine residues in the "core" region of asparagine-linked oligosaccharides. The CSL undergoes two stages of post-translational modification which result in an increase in its Mr from 24,000 to 26,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. We have determined that the lectin undergoes hydroxylation of proline and lysine and that the hydroxylysine is glycosylated to form glucosylgalactosylhydroxylysine (GlcGalHyLys). CSL metabolically labeled with [3H]lysine and [3H]proline contains hydroxylated forms of proline and lysine. The mature form of the lectin can also be metabolically labeled with [3H]galactose. alpha,alpha'-Dipyridyl, an inhibitor of collagen prolyl and lysyl hydroxylases, prevents the metabolic incorporation of [3H]galactose and the post-translational increases in the Mr of the CSL, indicating that both events are dependent upon hydroxylation of proline and lysine. Virtually all of the hydroxylysine present in the CSL is recovered as glucosylgalactosylhydroxylysine after alkaline hydrolysis. The post-translational modifications of the CSL place it in a select family of secreted proteins which contain collagen-like sequences, including the pulmonary surfactant proteins, complement component C1q, and the 18 S asymmetric form of acetylcholinesterase.